Small but mighty – study highlights the abundance and importance of the ocean’s tiniest inhabitants

Larger plankton have been used for decades to monitor ecosystem productivity and biodiversity, but four UK plankton surveys – including the Marine Biological Association’s Continuous Plankton Recorder survey – have also sampled tiny plankton in the past 14 years.

The researchers involved in the current study used the results of those surveys, which focused on the English Channel and Scottish coast, to investigate six groups of tiny plankton including two groups of heterotrophic bacteria.

Doing that involved a combination of flow cytometry – a laser-based technique used to detect and analyse the chemical and physical characteristics of cells or particles – and light microscopes.

This provided evidence of the abundance of tiny plankton, with that data then being cross-referenced against known changes in environmental conditions to assess how they were being impacted.

As a result, the researchers have recommended that tiny plankton groups should be used to inform biodiversity indicators that meet policy obligations under the EU Marine Strategy Framework Directive (MSFD), (Oslo-Paris Convention) OSPAR strategies, and the UK Marine Strategy.

They have also called for long-term monitoring of tiny plankton across multiple sites to ensure that policy decisions are based on accurate local and global evidence. 

Study co-lead Dr Rowena Stern, a CPR Research Fellow at the Marine Biological Association (MBA), added:

“We have been able to connect these tiny plankton to meaningful indicators for policy use by measuring how human-driven environmental pressures affect the timing of their growth. This has only been possible by taking consistent, long-term measurements of these types of plankton.”